Use of micellar solution as an emulsion breaker

ABSTRACT

Production of formation fluids through a well bore from a hydrocarbon-bearing subterranean formation having a water and hydrocarbon emulsion blockage surrounding the well bore is restored by injecting about 1 to about 500 gallons per vertical foot of hydrocarbon-bearing formation of micellar dispersion into the formation to &#39;&#39;&#39;&#39;solubilize&#39;&#39;&#39;&#39; the emulsion. The micellar dispersion is comprised of a surfactant having an average equivalent weight of 350-525.

United States Patent 1191 Webb Nov. 13, 1973 [54] USE ()F'MICELLARSOLUTION s AN 2,331,594 10/1943 13lai1',.lr. ..L 166/305 ux EMULSIONBREAKER 2,356,205 8/1944 Blair, Jr. et al. 252/8.55 2,369,831 2/1945Jones et al. 252/8.55 Inventor: Thomas 0- W C sp y 3,185,217 5 1965Brooks, Jr. et al.. 166/305 x 3,254,714 6/19 6 Gogarty et al. 166/274[731 Ass'gnee' 2 83 Fmdlay 3,402,770 9/1968 Messenger 166/305 R [22]Filed: 1971 Primary Examiner-Stephen J. Novosad [21] Appl' NO; 192,710Attorney-Joseph C. Herring et al.

Related U.S. Application Data Division of Ser. No. 20,042, March 16,1970, Pat. No. 3,684,015, which is a continuation-in-part of Ser. No.762,140, Sept. 24, 1968, Pat. No. 3,554,289.

U.S. Cl 166/305 Int. Cl E2lb 43/25 Field of Search.'...'..,. 166/305 R,306, 273-275,

References Cited UNITED STATES PATENTS l/l97l Webb 166/305 R [57]ABSTRACT hydrocarbon-bearing formation of micellar dispersion into theformation to solubilize the emulsion. The rnicellar dispersion iscomprised of a surfactant having an average equivalent weight of350-525.

4 Claims, No Drawings 1 USE OF MICELLAR SOLUTION AS AN EMULSION BREAKERThis application is a divisional of my copending application Ser. No.20,042 filed Mar. 16, 1970, now US.

Pat. No. 3,684,015, which is a continuation-in-part of 5 my copendingapplication Ser. No. 762,140, filed Sept. 24, 1968, now U.S. Pat. No.3,554,289.

BACKGROUND OF THE INVENTION -may stop altogether. Such can be caused byan emulsion block in the hydrocarbon-bearing formation, i.e., a viscousemulsion of water and hydrocarbon is formed around the well bore andadversely affects the advance of hydrocarbon to the well bore.

The prior art teaches that surfactants suspended in a .carrier, such ascrude oil or water, are useful to overcome the emulsion blockage. Such aprocess has proved satisfactory in many cases. in some cases, blockageis characteristic of a-oneway emulsion blockage, i.e., fluid can bepumped without difficulty into the formation but when the formation isrestored to production, the well will not produce. The so-called nativeemulsion is sometimes characteristic of this phenonemon.

Applicant has discovered that emulsion blockage in the formation canberemoved by injecting a sufficient amount of a micellar dispersion intothe formation to solubilize the emulsion. Once the emulsion issolubilized, the formation'is returned toproduction. Increases inhydrocarbon production are realized. The term solubilization as usedherein is broadly but not specifically meant to include take-up orpartial take-up of the emulsion by emulsification or sorption by themicellar dispersion to substantially overcome the adversity imparted bythe emulsion to the flow of hydrocarbon within the formation.

DESCRIPTION OF Ti -IE INVENTION The term micellar dispersion as usedherein is meant to include micellar solutions, microemulsions,transparent? emulsions (Blair,Jr. et al., US. Pat. No. 2,356,205),aqueous soluble oils and micellar solution technology taught in C. G.Sumner, Claytons The Theory f Emulsions and Their Technical Treatment,th Edition, pp. 315-320 (1954). Specific examples of useful micellarsolutions include those defined in U.S. Pat. Nos. 3,254,714 and3,275,075 to Gogarty et al.;

of hydrocarbon, about 10 percent to about 95 percent aqueous medium, atleast about 4 percent surfactant, about 0.01 to about 20 percentcosurfactant, (also identified as cosolubilizer and semi-polar organiccompound), and about 0.001 to about 5 percent or .more (weight percentbased on aqueous medium) of electrolyte. The micellar dispersioncontains at least about 5 percent aqueous medium.

The micellar dispersion can be oil-external or waterexternal. Where theemulsion blockage is oil-external, it is preferred to use anoil-external micellar dispersion. However, where the emulsion blockageis waterexternal, a water-external micellardispersion can be effectivelyused.

Examples of hydrocarbon useful in the micellar dis-.

persion include crude oil, partially refined fractions of crude oil,refined fractions of crude oil, synthesized hydrocarbons, etc. Specificexamples of such hydrocarbons include side cuts from crude columns,crude column overheads, gas oils, kerosenes, heavy naphthas, naphthas,straight-run gasoline, liquefied petroleum gases, propane, pentane,heptane, decane, dodecane, cyclohexane, aryl compounds, substituted arylcompounds, etc. Preferably, the hydrocarbon is one locally available andcan be characteristic of the hydrocarbon within the particular formationbeing treated. Unsulfonated hydrocarbon within a-petroleum sulfonate,e.g., unsulfonated gas oils, are useful as the hydrocarbon.

The aqueous medium can be soft, brackish, or brine water. When theaqueous medium contains ions, it is preferred that these ions becompatible or characteris' tic of the ions within the formation fluids.

Useful surfactants within the micellar dispersion include nonionic,cationic and anionic surfactants. Specific examples include thosesurfactants taught in US. Pat. No. 3,497,006 to Jones et al. Preferably,the surfactant is a petroleum sulfonate, also known as alkyl arylnaphthenic sulfonate. A particularly useful sulfonate is a monovalentcation containing sulfonate, e.g., sodium and ammonium petroleumsulfonate. Preferably the petroleum sulfonate has an average equivalentweight within the range of about 350 to about 525 and more preferablyabout 390 to about 460. The surfactant can be a mixture of two or moreof low, medium, and high average equivalent weight sulfonates or amixture of two or more different surfactants.

The cosurfactant useful with this invention includes alcohols, amides,amino compounds, esters, aldehydes, ketones, and like materialscontaining from one to about 20 or more carbon atoms. Preferably, thecosurfactant contains about three to about 16 carbon atoms. Specificexamples include alcohols such as isopropa- 1101, nand iso-butanol, amylalchols such as n-amyl al- 3,307,628 to Sena and US. Pat. No. 3,497,006to Jones et al. Micellar dispersions differ in many ways from emulsions,basically the micellar dispersion is thermodynamically. stable andgenerally transparent whereas emulsions are not thermodynamically stablesystems and are generally opaque.

The micellar dispersion is composed of hydrocarbon, aqueous medium, andsurfactant. Cosurfactant(s) and electrolyte(s) can optionally beincorporated within the micellar dispersion. Examples of volume amountsinclude about '4 percent to about 80 percent or more cohol, land2-hexanol, land 2-octan0l, decyl alcohols, dodecyl alcohols, etc., andalkaryl alcohols such as p-nonylphenol, alcoholic liquors such as fuseloil, compounds such as 2-butoxy-ethanol and like materials. Preferably,the cosurfactant is present in volume amounts of about 0.1 to about 5percent. Mixtures of two or more cosurfactants are also useful.

Electrolytes useful within the micellar dispersion include inorganicsalts, inorganic acids, inorganic bases, organic acids, organic basesand organic salts. Preferably, the electrolyte is compatible with theions within the formation fluids. Specific examples of electrolytesinclude sodium hydroxide, sodium chloride, sodium sulfate, hydrochloricacid, sulfuric acid, and electro- 3 lytes taught in US. Pat. Nos.3,330,343 to Tosch et al. and 3,297,084 to Gogarty et al. Additionally,the electrolyte can be the salts or ions within the aqueous medium,e.g., within brine or brackish water. The type and concentration ofelectrolyte will depend on the aqueous medium, surfactant, cosurfactant,hydrocarbon, and the reservoir conditions, including temperature of thereservoir.

When the emulsion blockage contains a high ionic content, it ispreferred that the micellar dispersion be designed to have a highaffinity for brine. For example, the micellar dispersion can be designedwith a lower average equivalent weight surfactant and/or a minimumamount of electrolytesuch can impart to the micellar dispersion a highbrine affinity or a high solubilization potential for an emulsioncontaining a high brine content. Also, where the emulsion blockage iswater-external, it may be desirable to design the micellar dispersion tobe more water-like in character and to have a high affinity for theemulsion. However, where the emulsion blockage is oil-external, it maybe desired to design the micellar dispersion to have a high affinity forhydrocarbon and thus the components within the micellar dispersion arechosen to impart a more oleophilic character to the micellar dispersion.

The amount of micellar dispersion injected into the formation should besufficient to solubilize substantially the emulsion causing the emulsionblockage. Certain factors which will determine the amount of micellardispersion injected include: (1) the'permeability of the formation(where the formation is less permeable, it may be desired to inject moreof the micellar dispersion), (2) porosity, i.e., where the porosity islarge, a larger amount of micellar dispersion is required, etc. However,a volume about equal to or in excess of the volume of emulsion is aboutthe maximum amount of micellar dispersion useful with the invention,from an economical basis. Generally, about 1 to about 500 gallons pervertical foor of hydrocarbon-bearing formation is useful to solubilizethe emulsion.

After the micellar dispersion is injected into the formation, it ispermitted to remain in contact for a sufficient period of time tosolubilize the emulsion. Such time will vary with the particularformation, the volume and character of the emulsion, and the characterof the micellar dispersion being injected. Examples of times includeabout 0.5 to about 24 hours.

Thereafter, the well is permitted to produce the formation fluidsthrough the well bore. In restoring the well to production, thesolubilized emulsion will be backflowed and thus removed uphole.

It is intended that the invention not be limited by the specificembodiments taught herein. Rather, all equivalents obvious to thoseskilled in the art are intended to be incorporated within the scope ofthis invention as defined within the specification and appended claims.

What is claimed is:

l. A method of restoring production of formation fluids from ahydrocarbon-bearing subterranean formation having a well borepenetrating the formation and wherein said formation is substantiallyblocked by a water and hydrocarbon emulsion, the method comprisl.injecting about 1 to about 500 gallons of micellar dispersion pervertical foot of hydrocarbon-bearing formation into the formation, themicellar dispersion comprised of at least 5 percent aqueous medium andcontaining petroleum sulfonate having an average equivalent weightwithin the range of about 390 to about 460,

2. permitting the micellar dispersion to solubilize the emulsion, and

3. returning the well to production.

2. A method of restoring production of formation fluids from ahydrocarbon-bearingsubterranean formation having a well bore penetratingtherein and wherein the formation is substantially blocked by a waterand hydrocarbon emulsion, the method comprising:

1. injecting into the formation about i to about 500 gallons pervertical foot of hydrocarbon-bearing formation of a micellar dispersioncomprised of hydrocarbon, a cosurfactant which is an alcohol(s)containing one to about 20 carbon atoms, and petroleum sulfonate havingan average equivalent weight of about 350 to about 525, and aqueousmedium,

2. permitting the micellar dispersion to remain in the formation untilthe emulsion is substantially solubilized by the micellar dispersion,and

3. returning the well to production.

3. A method of restoring production of formation fluids from ahydrocarbon-bearing subterranean formation having a well borepenetrating therein and wherein the formation is substantially blockedby a water and hydrocarbon emulsion, the method comprising:

1. injecting into the formation about 1 to about 500 gallons pervertical foot of hydrocarbon-bearing formation of a micellar dispersioncomprised of hydrocarbon, petroleum sulfonate having an averageequivalent weight within the range of from about 390 to about 460, andaqueous medium,

2. permitting the micellar dispersion to remain in the formation untilthe emulsion is substantially solubilized by the micellar dispersion,and

3. returning the well to production.

4. A method of restoring production of formation fluids from ahydrocarbon-bearing subterranean formation having a well borepenetrating therein and wherein the formation is substantially blockedby a water and hydrocarbon emulsion, the method comprising:

1. injecting into the formation about 5 to about 250 gallons pervertical foot of hydrocarbon-bearing formation of the micellardispersion comprised of hydrocarbon, petroleum sulfonate having anaverage equivalent weight of about 350 to about 525, and aqueous medium,

2. permitting the micellar dispersion to remain in the formation untilthe emulsion is substantially solubilized by the micellar dispersion,and

3. returning the well to production.

2. permitting the micellar dispersion to solubilize the emulsion, and 2.A method of restoring production of formation fluids from ahydrocarbon-bearing subterranean formation having a well borepenetrating therein and wherein the formation is substantially blockedby a water and hydrocarbon emulsion, the method comprising: 2.permitting the micellar dispersion to remain in the formation until theemulsion is substantially solubilized by the micellar dispersion, and 2.permitting the micellar dispersion to remain in the formation until theemulsion is substantially solubilized by the micellar dispersion, and 2.permitting the micellar dispersion to remain in the formation until theemulsion is substantially solubilized by the micellar dispersion, and 3.returning the well to production.
 3. returning the well to production.3. A method of restoring production of formation fluids from ahydrocarbon-bearing subterranean formation having a well borepenetrating therein and wherein the formation is substantially blockedby a water and hydrocarbon emulsion, the method comprising:
 3. returningthe well to production.
 3. returning the well to production.
 4. A methodof restoring production of formation fluids from a hydrocarbon-bearingsubterranean formation having a well bore penetrating therein andwherein the formation is substantially blocked by a water andhydrocarbon emulsion, the method comprising: